660 MW燃煤机组脱硝系统优化改造

Optimization of Denitrification System for a 660 MW Coal-fired Unit

脱硝系统烟气流场分布特性与氨烟混合特性直接影响脱硝效率和氨逃逸。一660MW机组原有脱硝系统存在催化剂入口烟气流速分布不均、喷氨母管氨空混合性差、喷氨格栅后氨烟混合性差、喷氨量控制不够精细等问题。基于数值模拟结果,提出了脱硝系统内安装导流元件、喷氨母管内加装氨空混合器、喷氨格栅后加装氨烟混合器、喷氨格栅实施分区控制的优化改造方案。改造后的现场实验结果表明,脱硝系统优化后,催化剂入口烟气流速分布、烟温分布的均匀性均较好,催化剂进出口NOx的质量浓度分布偏差均较小,660MW负荷下喷氨量比改造前下降34.5%。

The flow field of the flue gas and the mixing of ammonia with the flue gas affect the efficiency of denitrification and ammonia escape. The denitrification system of a 660 MW unit met some problems, including the velocity distribution of the flue gas was ununiform, the mixing of air and ammonia in the main pipe was poor, the mixing of flue gas and ammonia was poor in the downstream of the injection grid, the control of ammonia injection was not precise enough, etc. Based on the results of the numerical simulation, this paper proposed to install flow controlling device, mixer of air and ammonia, mixer of flue gas and ammonia, sub-regional controller to improve the performance of the denitrification system. The experimental results after the optimization showed that the distribution of the velocity and temperature field of the flue gas at the inlet of the catalyst was improved, the uniformity of NOxmass concentration distribution at the inlet of the catalyst was decreased, and under 660 MW load condition, the quantity of ammonia used for the denitrification system was decreased by 34.5%.